Production and use of octafluoropropane

Abstract

Octafluoropropane is produced by a process comprising a step (1) of reacting hexafluoropropene with hydrogen fluoride in a gas phase at a temperature of from 150 to 450° C. in the presence of a fluorination catalyst to obtain 2H-heptafluoropropane and a step (2) of reacting 2H-heptafluoropropane obtained in step (1) with fluorine gas in a gas phase at a temperature of from 250 to 500° C. in the absence of a catalyst to obtain octafluoropropane. High-purity octafluoropropane is obtained which can be used in a process for producing a semiconductor device.

Description

The present invention relates to a process for producing octafluoropropane, an octafluoropropane product, and uses thereof.Octafluoropropane is used, for example, as a dry-etching or cleaning gas in the process for producing a semiconductor device. With respect to the production methods thereof, the following methods are known:(1) a method of performing a direct fluorination reaction between hexafluoropropene and fluorine gas (see, Japanese Examined Patent Publication No. 62-61572 (JP-B-62-61572)),(2) a method of performing an electrolytic fluorination of hexafluoropropene in hydrogen fluoride (see, Japanese Examined Patent Publication No. 62-61115 (JP-B-62-61115)),(3) a method of reacting hexafluoropropene with fluorine in the presence of a catalyst (see, Japanese Examined Patent Publication No. 1-45455 (JP-B-1-45455)), and(4) a method of reacting hexafluoropropene with a high-order metal fluoride (see, Japanese Examined Patent Publication No. 62-54777 (JP-B-62-54777)).However, in ...

AI Technical Summary

Benefits of technology

The present invention provides a method for producing high-purity octafluoropropane, which is a useful gas for the production of semiconductor devices. The method involves a two-step process involving the reaction of hexafluoropropene with hydrogen fluoride in a gas phase at a temperature of 150 to 450 degrees Celsius in the presence of a fluorination catalyst to obtain 2H-heptafluoropropane, followed by the reaction of 2H-heptafluoropropane with fluorine gas in a gas phase at a temperature of 250 to 550 degrees Celsius in the absence of a catalyst to obtain octafluoropropane. The resulting octafluoropropane has a high purity of 99.999 vol% or more, with a low content of compounds having a chlorine atom within the molecule and cyclic compounds. The invention also provides an octafluoropropane product with a high purity of 99.9995 vol% or more. The method and product of the invention can be used in various processes for producing semiconductor devices.

Problems solved by technology

However, in these methods, by-products such as tetrafluoromethane (CF.sub.4) and hexafluoroethane (C.sub.2 F.sub.6) are produced due to cleavage, C.sub.6 F.sub.12 and C.sub.6 F.sub.14 are produced due to radical addition, and a 4-membered ring is produced due to cyclization addition, for example, and as a result, the yield of and selectivity for the objective octafluoropropane decrease.

Furthermore, some compounds in these impurities are difficult to separate by distillation and, in turn, high-purity octafluoropropane can hardly be obtained.

Particularly, in the case of using hexafluoropropene as the starting material, chloropentafluoroethane (CFC-115) contained as an impurity scarcely reacts with fluorine gas and mostly remains in the objective octafluoropropane and since this impurity compound can hardly be separated by distillation, due to the similar boiling points, production of high-purity octafluoropropane is difficult.